Operating machinery

Abstract

The present disclosure relates to a work machine. The work machine includes an engine for driving a main work unit. At least one hydraulically driven auxiliary work unit is powered by a hydraulic pump. Both the engine and the electric motor provide power to the hydraulic pump via a planetary gear set, which adds the power inputs from the engine and the electric motor. Thereby, the pump speed of the hydraulic pump is decoupled from the engine speed of the engine.

Description

Technical Field

[0001] The present disclosure relates to a work machine of the type having a main working unit driven by an engine and having an auxiliary working unit driven hydraulically. Background Art

[0002] Work machines of this type may include, for example, wheel loaders, backhoes, skid steers, and other machines in which a hydraulically-driven auxiliary work unit can provide heavy loads to the engine and can be used while the drive train of the work machine is accelerating or decelerating.

[0003] In the example of a wheel loader, the main working unit may be the wheels that propel the wheel loader on the ground, and the hydraulically driven auxiliary working units may include a lift arm that raises and lowers a bucket or forks to engage a load to be lifted, moved, and unloaded by the wheel loader. Traditionally, a wheel loader includes a hydraulic pump that is driven by the engine to generate hydraulic power for the hydraulically driven auxiliary working units. With this arrangement, if additional hydraulic power is needed, the engine speed is increased to increase the speed of the hydraulic pump and, therefore, the hydraulic power available to the auxiliary working units.

[0004] One disadvantage of this arrangement is that the engine speed necessary to provide the required hydraulic power may be higher than the engine speed currently required to power the main working unit, causing the engine to operate inefficiently. Summary of the invention

[0005] The present disclosure provides improvements to the construction and operation of a work machine to enable the speed of a hydraulic pump to be decoupled from the speed of the engine, thereby enabling the engine to operate more efficiently.

[0006] In one embodiment, a work machine may include an engine, a main work unit, and a transmission configured to transfer power from the engine to the main work unit. The work machine may include at least one hydraulically driven auxiliary work unit and a hydraulic pump configured to provide power to the at least one hydraulically driven auxiliary work unit. The work machine may include an electric motor and a planetary gear set. The planetary gear set includes a first power input connected to the engine, a second power input connected to the electric motor, and a power output connected to the hydraulic pump.

[0007] Preferably, the drive train comprises a gearbox configured to transfer power from the engine to the one or more of the ground engaging units.

[0008] Preferably, the gearbox is an electronic continuously variable transmission.

[0009] Preferably, the working machine is a wheel loader, and the at least one hydraulically driven auxiliary working unit comprises a lifting arm of the wheel loader.

[0010] Preferably, the planetary gear set includes: a sun gear, the electric motor is connected to the sun gear to limit the second power input; a plurality of planetary gears connected to a gear carrier, the planetary gears engage the sun gear and can move around the sun gear, the engine is connected to the gear carrier to define the first power input; and a ring gear surrounding the planetary gears and engaging the planetary gears, the ring gear being connected to the hydraulic pump to limit the power output.

[0011] Preferably, the engine and the electric motor are configured such that a maximum value of the first power input from the engine is greater than a maximum value of the second power input from the electric motor.

[0012] In another embodiment, a method for controlling such a working machine is provided. The method may include the following steps:

[0013] (a) using an engine to provide a first power input to the planetary gear set;

[0014] (b) providing a second power input to the planetary gear set using an electric motor; and

[0015] (c) The first power input and the second power input are added by a planetary gear set and a power output is provided from the planetary gear set to the hydraulic pump.

[0016]

[0011] Numerous objects, features and advantages of the embodiments set forth herein will become readily apparent to those skilled in the art when the following disclosure is read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a side view of a working machine in the form of a wheel loader.

[0018] Figure 2 yes Figure 1 Schematic diagram of a first embodiment of a work machine in which power for the electric motor is provided by a generator driven by a gearbox of the work machine.

[0019] Figure 3 yes Figure 1 Schematic diagram of a second embodiment of a work machine, in which the power for the electric motor is provided by a battery carried by the work machine.

[0020] Figure 4 is a schematic diagram of a planetary gear set.

[0021] Figure 5 is with Figure 1 The engine, motor and hydraulic pump of the working machinery are connected Figure 4 Schematic diagram of a planetary gear set.

[0022] Figure 6 yes Figure 1 Schematic diagram of a drive train of a working machine including an eIVT gearbox.

[0023] Figure 7 is a schematic diagram of a controller for a work machine and the associated inputs and outputs. DETAILED DESCRIPTION

[0024] Referring now to the drawings, and in particular to Figure 1 , a work machine is shown in side view and is generally designated by the reference numeral 10 . Figure 1 A wheel loader machine 10 is shown. The systems disclosed herein are applicable to wheel loaders, backhoes, skid steers, and other work machines of the type having a main work unit driven by an engine and having hydraulically driven auxiliary work units. These systems are particularly useful for work machines in which the hydraulically driven auxiliary work units are capable of overloading the engine and can be used while the drive train of the work machine is accelerating or decelerating. In one embodiment, each of the main work unit and the hydraulically driven auxiliary work unit can be capable of fully loading the engine.

[0025] Work machine 10 includes a frame 12 supported off ground 14 by front ground engaging units 16 and rear ground engaging units 18. The illustrated ground engaging units 16 and 18 are wheeled ground engaging units, but it will be appreciated that tracked ground engaging units may also be used.

[0026] The engine 20 is supported by the frame 12, and the engine 20 may be, for example, a diesel-driven internal combustion engine. The cab 22 may be located on the frame 12, in front of the engine 20. The lifting arm 24 is pivotably supported by the frame 12 at a pivot 26, and hydraulic lifting cylinders 28 and 29 are connected between the frame 12 and the lifting arm 24 to pivot the lifting arm 24 up and down about the pivot 26. The work tool 30 is pivotably attached to the lifting arm 24 at a second pivot 32, and is pivoted relative to the lifting arm 24 by a hydraulic pivot cylinder 34, and the work tool 30 may be, for example, a bucket or a fork.

[0027] In operation, work machine 10 will engage various loads with work implement 30, raise the load, move the load over the ground to a second location, and unload the load. Figure 2 and Figure 3 As further schematically shown in FIG. 1 , the engine 20 may provide direct mechanical drive to the ground engaging units 16 , 18 via a drive train 36 .

[0028] The drive train 36 may include, for example, a gearbox 40, a front axle 42, and a rear axle 44. The front axle 42 may drive the front wheels 16. The rear axle 44 may drive the rear wheels 18. The gearbox 40 is configured to transfer power from the engine 20 to the drive wheels at a variety of gear ratios.

[0029] In an embodiment of the work machine 10 as a wheel loader, one or more of the front ground engaging unit 16 and the rear ground engaging unit 18 may be described as a main working unit 19, and the drive train 36 may be described as being configured to transfer power from the engine 20 to the main working unit 19 to propel the work machine 10 on the ground 14.

[0030] In the embodiment of the work machine 10 being a wheel loader, the lift arm 24 , the work implement 30 , and the associated hydraulic lift cylinders 28 and 29 and the hydraulic pivot cylinder 34 may be collectively referred to as a hydraulically driven auxiliary work unit 46 .

[0031] As in Figure 2 , Figure 3 and Figure 7 As schematically shown in FIG. 1 , the hydraulic pump 48 provides hydraulic power to a hydraulic system 50 , which can provide power to the hydraulically driven auxiliary working unit 46 and other hydraulic components of the work machine 10 .

[0032] The work machine 10 may also include an electric motor 52. The present disclosure provides a system that combines the power inputs from the engine 20 and the electric motor 52 to power the hydraulic pump 48. The primary power source may be the engine 20, and the electric motor 52 may be used to provide additional power as needed to control the power directed to the hydraulic pump 48 in a manner different from simply changing the speed of the engine 20. This decouples the pump speed of the hydraulic pump 48 from the engine speed of the engine 20. This combination of power inputs is achieved with a planetary gear set 54.

[0033] like Figure 4 As schematically illustrated in FIG. 1 , the planetary gear set 54 includes a sun gear 56, a plurality of planetary gears 58 connected to a carrier 60, and a ring gear 62. The planetary gears 58 are engaged with the sun gear 56 and can move around the sun gear 56. The ring gear 62 surrounds and engages the planetary gears 56 and can rotate around the planetary gears 58 and the sun gear 56. Figure 5 As further schematically illustrated in FIG. 1 , engine 20 may be connected to carrier 60 to define a first power input 64 schematically indicated by an arrow referenced at 64. Electric motor 52 may be connected to sun gear 56 to define a second power input 66 schematically indicated by an arrow referenced at 66. Ring gear 62 may be connected to hydraulic pump 48 to define a power output 68 schematically indicated by an arrow referenced at 68.

[0034] The electric motor 52 driving the sun gear 56 acts as a transmission to regulate the power output 68 and thus the pump speed of the hydraulic pump 48 .

[0035] As further described below, the planetary gear set 54 is configured to add a first power input 64 from the engine 20 and a second power input 66 from the motor 52 to drive the hydraulic pump 48. As further described below, this enables the pump speed of the hydraulic pump 48 to be controlled by controlling the motor speed of the motor 52.

[0036] exist Figure 2 In an embodiment, the gearbox 40 can drive the generator 72 to generate DC power. The power inverter 74 can convert the DC power into AC power, which is directed to the motor 52, which can be an electric motor driven by the AC power. The DC power can also be extracted from a power bus associated with the gearbox 40, which can be an eIVT transmission as further described below.

[0037] exist Figure 3 In an alternative embodiment, the work machine 10 may include a battery 76, and the DC power from the battery 76 may be passed through a power conversion device 78, which converts the DC power to AC power to drive the motor 52. The battery 76 may be recharged by reverse operation of the motor 52. The power conversion device 78 may be a bidirectional device. The power conversion device 78 may also include parallel inverter and rectifier channels so that the DC power flowing from the battery 76 is inverted to produce AC power for the motor 52, and so that the AC power flowing from the motor 52 in reverse operation is rectified for storage in the battery 52.

[0038] In one embodiment, the battery 76 may be sized similar to batteries currently used in hybrid vehicles where it is desirable to recharge the battery during intervals of maximum hydraulic demand. In another embodiment, the battery 76 may be larger, similar to batteries currently used in plug-in hybrid vehicles, and the battery may be sized to perform multiple hydraulic operations without recharging between intervals of maximum hydraulic demand.

[0039] The transmission 40 may be an electronic continuously variable transmission (eIVT) such as disclosed, for example, in U.S. Patent Application Publication No. 2018 / 0149247 to Rekow et al., the details of which are incorporated herein by reference.

[0040] Now refer to Figure 6, depicting various components of the drive train 36. For example, the engine 20 may provide mechanical power (e.g., via a rotating shaft) to the gearbox 40, which may be in the form of an eIVT. The engine 20 may also provide mechanical power to an infinitely variable power (IVP) machine 80, which may include one or more IVP machines (e.g., an electric motor and a generator, or a hydrostatic machine with a hydrostatic motor and an associated pump). The gearbox 40 may additionally receive mechanical power from the IVP 80.

[0041] The transmission 40 may include various clutches 82 and brakes 84 that may be controlled by various actuators 86. The actuators 86, in turn, may be controlled by a transmission control unit ("TCU") 88 (or another controller), which may receive various inputs from various sensors or devices (not shown) via a CAN bus (not shown) of the work machine 10. The transmission 40 may include one or more output shafts 89a, 89b for transmitting mechanical power from the transmission 40 to various other components (e.g., differential drive shafts). In certain embodiments, additional gear sets (e.g., range gear sets) may be inserted between the transmission 40 and other parts of the work machine 10 (e.g., differential drive shafts). In certain embodiments, the transmission 40 may also provide power directly to other parts of the work machine 10 (e.g., via direct drive shafts 89b).

[0042] Figure 7 Control system

[0043] like Figure 7 As schematically illustrated in FIG. 1 , the work machine 10 includes a control system 90 including a controller 92. The controller 92 may be a component of a transmission control unit 88 of the transmission 40 or a component of another machine controller of the work machine 10, or it may be a separate control module. In any case, the controller 92 may work in conjunction with the transmission control unit 88 so that the engine speed of the engine 20 is set by the transmission control unit 88 primarily based on the engine speed required to power the drive train constituting the main work unit 19, and so that the controller 92 controls the motor speed of the electric motor 52 to control the pump speed of the hydraulic pump 48, thereby controlling the hydraulic power provided to the hydraulic components constituting the hydraulically driven auxiliary work unit 46. The controller 92 may be mounted at a control panel in the cab 22.

[0044] The controller 92 is configured to receive input signals 118 from a hydraulic system control input 120 located in the cab 22. The control input 120 may be, for example, a joystick control 120 for operating the lift arm 24 and the work tool 30. Typically, such a joystick control 120 may be pulled back or pushed forward to raise or lower the lift arm 24, respectively. The joystick control 120 may be moved left or right to rotate the work tool 30 relative to the lift arm 24. A position sensor integrated in the joystick control 120 generates the input signal 118 that is sent to the controller 92. The algorithm contained in the software in the controller 92 may then determine the power required for the hydraulic system and the corresponding motor speed required for the electric motor 52 to provide the required power to the hydraulic pump 48.

[0045] Controller 92 will generate a control signal, such as control signal 52C, that is directed to motor 52 to control motor speed.

[0046] The controller 92 will also generate control signals for controlling the operation of the various hydraulic actuators, such as control signals 28C, 29C and 34C. Figure 7 These control signals are schematically indicated in the figure by dashed lines connecting the controller 92 to the various actuators, with arrows indicating the flow of command signals from the controller 92 to the respective actuators. It should be understood that the various actuators (such as actuators 28, 29, and 34) disclosed herein may be hydraulic piston-cylinder units, and that the electronic control signals from the controller 92 will actually be received by the electro-hydraulic control valves associated with the actuators, and the electro-hydraulic control valves will control the flow of hydraulic fluid into and out of the respective hydraulic actuators in response to the control signals from the controller 92 to control the actuation of the hydraulic actuators.

[0047] The control signals 28C and 29C sent to the lifting cylinders 28 and 29 (see Figure 7 ) extends or retracts the lift cylinders 28 and 29 in response to input signals 118 from the joystick control 120 to raise and lower the lift arm 24. The control signal 34C sent to the pivot cylinder 34 (see Figure 4 ) controls the pivoting of the work tool 30 relative to the lift arm 24. The control signal is generated at least in part in response to the input signal 118.

[0048] The controller 92 includes or may be associated with a processor 94, a computer readable medium 96, a database 98, and an input / output module or control panel 100 having a display 102. An input / output device 104 such as a keyboard, joystick, or other user interface is provided so that an operator can input instructions to the controller. The input / output device 104 may include the joystick control 120 discussed above. It should be understood that the controller 92 described herein may be a single controller having all of the described functionality, or it may include multiple controllers, wherein the described functionality is distributed among the multiple controllers.

[0049] The various operations, steps or algorithms described in conjunction with the controller 92 may be implemented directly in hardware, in a computer program product 106 (such as a software module executed by the processor 94), or in a combination of the two. The computer program product 106 may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, or any other form of computer-readable medium 96 known in the art. An exemplary computer-readable medium may be coupled to the processor 94 so that the processor can read information from the memory / storage medium and write information thereto. In an alternative form, the medium may be integrated with the processor. The processor and the medium may reside in an application specific integrated circuit (ASIC). The ASIC may reside in a user terminal. In an alternative form, the processor and the medium may reside in a user terminal as discrete components.

[0050] As will be appreciated by those skilled in the art, the term "processor" as used herein may refer to at least general or special purpose processing devices and / or logic, including but not limited to microprocessors, microcontrollers, state machines, etc. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0051] exist Figure 7 , a hydraulic fluid supply system 50 is further schematically illustrated, which includes the previously mentioned hydraulic pump 48. The pump 48 takes hydraulic fluid from a tank 108 and provides pressurized hydraulic fluid to a hydraulic fluid supply line 110. The supply line 110 is connected to a first inlet of each of the electro-hydraulic directional and flow control valves 28V, 29V, and 34V associated with the first lift cylinder 28, the second lift cylinder 29, and the pivot cylinder 34.

[0052] The hydraulic fluid supply system 50 may include a pressure reducing valve 122 to control the pressure within the hydraulic fluid supply system 50. Exhaust from the pressure reducing valve 122 flows back to the tank 108 via a return line 124. The pressure reducing valve 122 may be an adjustable valve that may be adjusted via a command signal 122C from the controller 92.

[0053] Each of valves 28V, 29V, and 34V is shown as a three-position valve having a center position in which no flow passes through the valve, a left position in which fluid flows to a first outlet port, and a right position in which fluid flows to a second outlet port. Hydraulic fluid from each control valve flows to its corresponding hydraulic cylinder in a selected direction. Return fluid from the hydraulic cylinder flows through the corresponding control valve back to return line 112, which returns the hydraulic fluid to tank 108.

[0054] Each of valves 28V, 29V and 34V may be a proportional control valve, wherein, in addition to controlling the direction of flow, the valves also control the flow of hydraulic fluid in response to control signals received from controller 92. Alternatively, each of the hydraulic cylinders may have a separate flow direction control valve and a flow control valve associated therewith.

[0055] It will be appreciated that the two valves 28V and 29V may be combined into a single valve, thereby providing a split output to the two hydraulic cylinders 28 and 29, such that those cylinders operate in series.

[0056] The operation of the work machine 10 can be generally described as follows. The operator will direct two operations, each of which can place significant power demands on the machine. The first operation, referred to in this disclosure as the operation of the main work unit 19, can be, for example, directing the front wheels 16 and the rear wheels 18 to move the work machine 10 on the ground. This operation can be directed by a throttle control manually operated by the operator. The transmission control unit 88 of the eIVT transmission 40 can set the engine speed of the engine 20 at a preferred speed for efficient engine operation in response to the throttle position. The second operation, referred to in this disclosure as the operation of the auxiliary work unit 46, can be, for example, directing the operation of the lifting arm 24 and the work tool 30 via the hydraulic cylinders 28, 29 and 34. This second operation can be directed by the joystick control 120 described previously. The controller 92 can set the motor speed of the electric motor 52 in response to the input signal 118 from the joystick control 120. The controller 92 can also adjust the maximum hydraulic pressure in the hydraulic supply system 50 by adjusting the pressure reducing valve 122. Other specific examples of such operations are given below.

[0057] Examples:

[0058] The work tool 10 may be a wheel loader, and the planetary gear set 54 may include a sun gear 56 having twenty teeth and a ring gear 62 having seventy teeth. For a sun gear input, a ring gear output, and a fixed carrier, the planetary gear set may provide a speed ratio of -0.287. For a carrier input, a ring gear output, and a fixed sun gear, the planetary gear set may provide a speed ratio of 1.287. The following table shows the input power from the engine 10, the input power from the motor 52, and the output power to the hydraulic pump 48 under various operating conditions.

[0059] Table 1 illustrates the power flow when the hydraulic pump 48 is in standby mode and the battery 76 is not being charged. In the table, negative "power" numbers indicate power flowing out of (i.e., generated by) the specified component, and positive "power" numbers indicate power flowing into the specified component. Therefore, if the motor 52 is acting as a generator, the "power" of the motor 52 is a positive number, and if the motor is acting as a motor, the "power" of the motor 52 is a negative number. The "power" of the engine 20 is always a negative number, and the "power" of the hydraulic pump 48 is always a positive number.

[0060]

[0061] Table II illustrates the power flow when the hydraulic pump 48 is in standby mode and the battery 76 is being charged. In this example, the engine 20 is driven at various engine speeds as directed by the transmission control unit 88 to provide the power required to push the work machine 10 over the ground. The remaining power available from the engine is used to charge the battery.

[0062]

[0063]

[0064] Table III illustrates the power flow when the hydraulic pump 48 is operating at maximum hydraulic power output and the battery 76 is discharging to power the motor 52. In this example, the engine 20 is driven at various engine speeds as directed by the transmission control unit 88 to provide the power required to push the work machine 10 on the ground. At the same time, there is a large demand for power from the hydraulic system. The engine 20 meets this demand as much as possible, while the motor 52 provides any additional power required. Note that in this example, the engine 20 and the motor 52 are configured so that the maximum value of the power input from the engine 20 is greater than the maximum value of the power input from the motor 52.

[0065]

[0066]

[0067] How to operate

[0068] A method of operating work machine 10 may include the following steps:

[0069] (a) using the engine 20 to provide a first power input 64 to the planetary gear set 54;

[0070] (b) using the electric motor 52 to provide a second power input 66 to the planetary gear set 54; and

[0071] (c) The first power input 64 and the second power input 66 are summed by the planetary gear set 54 and a power output 68 is provided from the planetary gear set 54 to the hydraulic pump 48 .

[0072] The method may further include controlling the pump speed of the hydraulic pump 48 by controlling the motor speed of the electric motor 52. The controlling step may be performed using an automatic controller 92.

[0073] The method may further include:

[0074] Producing electricity using a generator 72 driven by the drive train 36; and

[0075] Electric power from the generator 72 is provided to the electric motor 52 .

[0076] The method may also include providing power to the electric motor 52 from a battery 76 carried by the work machine 10 .

[0077] Thus, it is seen that the apparatus and method of the present disclosure readily achieve the objects and advantages mentioned as well as those inherent therein. Although certain preferred embodiments of the present disclosure have been illustrated and described for the present purposes, those skilled in the art may make many changes in the arrangement and construction of the parts and steps, which changes are encompassed within the scope and spirit of the present disclosure as defined by the appended claims. Each feature or embodiment disclosed may be combined with any other feature or embodiment disclosed.

Claims

1. A working machine (10), comprising: Engine (20); Main working unit (19); a transmission system (36) configured to transmit power from the engine (20) to the main working unit (19); at least one hydraulically driven auxiliary working unit (46); a hydraulic pump (48) configured to provide power to the at least one hydraulically driven auxiliary working unit (46); Motor (52); as well as a planetary gear set (54) comprising a first power input (64) connected to the engine (20), a second power input (66) connected to the electric motor (52), and a power output (68) connected to the hydraulic pump (48), wherein the planetary gear set (54) is configured to add the first power input (64) from the engine (20) and the second power input (66) from the electric motor (52) to drive the hydraulic pump (48), so that the pump speed of the hydraulic pump (48) can be controlled by controlling the motor speed of the electric motor (52), The working machine also includes: A controller (92) is configured to control a pump speed of the hydraulic pump (48) by controlling a motor speed of the electric motor (52).

2. The working machine according to claim 1, further comprising: a generator (72) operatively connected to the drive train (36) and configured to generate electricity; and The electric motor (52) is connected to the generator (72) for receiving electric power from the generator.

3. The working machine according to claim 2, wherein: The transmission system (36) includes a gearbox (40) configured to transmit power from the engine (20) to the main working unit (19) at multiple gear ratios; and The generator (72) is driven by the gearbox (40).

4. The working machine according to claim 3, wherein: The controller (92) is a component of a transmission control unit (88) of the transmission (40).

5. The working machine according to claim 1, further comprising: Battery (76); and The electric motor (52) is connected to the battery for receiving electric power from the battery.

6. The working machine according to claim 5, further comprising: A DC-AC inverter connects the battery (76) to the electric motor (52).

7. The working machine according to claim 1, further comprising: Rack (12); as well as a plurality of ground engaging units (16, 18) supporting the frame off the ground (14), wherein the main working unit (19) comprises one or more of the ground engaging units (16, 18); wherein the engine (20) is supported by the frame (12); and The drive train (36) is configured to transfer power from the engine (20) to the one or more ground engaging units (16, 18) to propel the work machine (10) on the ground (14).

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